The demand for computers to be able to communicate with each other and share resources continues to increase. Wireless networking fulfills this demand without the time, cost, and inconvenience of running network cables. Furthermore, as is well understood, wireless networking affords much greater flexibility to computer users by enabling them to access a network without being tethered to a network connection.
While wireless computer networking has grown in popularity, at the same time, applications that require increasingly more network bandwidth also are becoming more popular. For example, Internet users increasingly access the Internet to download music, watch streaming video, and converse with other people using voice over Internet protocol (VoIP). In particular, conveying streaming video over a wireless network link can easily overburden the wireless connection by exceeding its throughput capability.
Most conventional wireless network access points employ a single transceiver equipped with one or more omnidirectional antennae. As shown in FIG. 1A, access point 100 includes two omnidirectional antennae 102a and 102b coupled via a diversity switch 104 to an access point controller 106. Many commercially available chipsets reference designs well-suited for access points incorporate a diversity switch. Access point controller 106 is connected via a communications line 108 to a network 110 and manages uplink data transmissions from wireless communication clients (not shown) received via antennae 102a and 102b, as well as downlink data conveyed over communication line 108 for transmission via antennae 102a and 102b. More specifically, access point 100 may be coupled to a broadband Internet or other WAN interface (not shown). Although diversity switch 104 is shown as a separate component, it is typically integrated within access point controller 106, and antennae 102a and 102b are selectively coupled to the access point controller through the diversity switch.
Access point controller 106 also controls diversity switch 104 to optimize communications between access point 100 and one or more clients (not shown). Because of the high frequency employed in wireless communications, e.g., 2.4 GHz or 5 GHz in wireless networks meeting the Institute of Electrical and Electronics Engineers (IEEE) 802.11 specifications, the wavelength of the wireless signals used for communication by access point 100 is on the order of a few centimeters. As a result, a shift in position of an access point antenna of only a few centimeters can significantly change the quality of signals received and transmitted between access point 100 and its clients. Thus, switching between antennae—even antennae incorporated in or attached to a relatively compact device—can appreciably affect communication between an access point and a client.
As is understood in the art, the best communication quality between an access point and a client will not always be provided by using the closer of the two antennae to the client for transmitting and receiving the signal. Signals from the nearer antenna might be blocked by one or more obstacles—even moving obstacles such as people, pets, or doors that are opening or closing—while the signal path for the other antenna fortuitously may be less affected or provide a stronger signal due to reflections of the signal from surfaces. The antenna that provides the best communication quality may change from time to time. Thus the communication quality available using each antenna may be evaluated periodically, or when packet retry rates or other variables indicate that communication quality with the antenna currently in use has deteriorated.
Similarly, many wireless communication protocols support a range of communication rates. As the communication rate is increased, the effective range of data communication may be reduced. Thus, communications between an access point and a nearby client may occur at a higher rate than between the access point and a client that is further away, or a client in a position where more obstacles interfere with the signal between the access point and the client. In particular, the IEEE 802.11b wireless communication protocol supports four different communication rates that may be selected for communication between the access point and the client. The newer IEEE 802.11g protocol includes twelve different rates that may be used. Currently available access points adjust the data rate depending on factors such as received signal strength indication (RSSI) or the number of packet transmit retries required, by cycling through the available rates in a trial and error approach, or using other methods to select the appropriate rate.
For example, FIG. 1B shows a wireless local area network (LAN) 111b in which access point 100 communicates with clients 112a and 112b within a communication area represented by a dash line 114b. In this simplified example, where there are no intervening obstructions or sources of interference, because access point 100 is closer to client 112a, access point 100 and client 112a are able to communicate with each other at a higher communication rate represented by a heavy dash line 116a, than with client 112b, which is barely within the communication area, wherein the lower communication rate with client 112b is represented by a dotted line 116b. 
Although an access point is able to reliably communicate with a more distant or a less optimally situated distant client by switching to a lower communication rate, data communication at the lower data rate may be unsatisfactory for the intended application. Furthermore, communication of a fixed amount of data at a low rate consumes more channel time, resulting in less time to communicate with other clients on the network.
To solve this problem, access points have been created that include multiple radio transceivers, each of which is coupled to a different directable antenna. However, using directable antennae that are directed toward (or in the optimum direction for) specific client locations sacrifices the coverage area available with an omnidirectional antenna in order to improve communication gain within the more narrow coverage areas served by the directable antennae. As a result, a client that may not have been able to workably communicate with an access point at a higher communication rate using an omnidirectional antenna at the access point, would be able to communicate with the access point at the higher communication rate using a directable antenna this is directed toward the client (or in the optimum direction for that client).
Multiple-radio transceiver access points with directable antennae unfortunately present a number of disadvantages. First, equipping the access point with multiple transceivers and the logic needed to control those transceivers understandably makes the access point much more costly to manufacture. As a result, multiple-radio transceiver access points may be too costly for in-home wireless networks or even for small business wireless networks.
Second, for reasons previously described with regard to signals being obstructed by or reflected by objects in the communication area, setting up the access point to properly direct the directable antennae may be difficult. Similarly, because obstacles move, or the client computers may be moved, and due to other factors, it may be inconvenient or impractical to adjust the directing of the antennae to a fixed orientation.
Third, although facilitating faster communication with some clients, using directable antennae may result in a limited coverage area that does not allow some clients to communicate with the access point. For example, as shown in FIG. 1C, an access point 100c includes a directable antenna (not shown) that covers a communication area 120. The directable antenna enables access point 100c to communicate at a higher communication rate (represented by a heavy dash line 116c) with client 112b, which is in communication area 120 than was previously possible using only an omnidirectional antenna. The omnidirectional antenna only enabled communication at a substantially lower rate, as represented by dotted line 116b. However, client 112a, which had been able to communicate with access point 100 (FIG. 1B) at a relatively high communication rate, is now outside communication range 120 of access point 100c. Even if another transceiver with another directable antenna were added to access point 100c to facilitate communication with client 112a, there still may be clients without service. For example, even if access point 100c were able to communicate with both clients 112a and 112c, a client 112c that is well within the potential communication range of an omnidirectional antenna represented by a dotted line 114c would be unable to communicate with access point 100c, unless yet another directable antenna and another transceiver were added to the access point to service client 112c. 
Fourth, using directable antennae with a multiple-radio transceiver access point can create overhead problems that may undermine the benefit of the multiple-radio transceiver access point. For instance, in the example of access point 100c (in FIG. 1C) having multiple directable antennae to communicate with clients 112a and 112b, access point 100c will be able to suitably direct messages that are directed specifically to each of the clients. However, if there are broadcast messages for all stations, those messages will have to be transmitted multiple times, and sent on each of the transceivers/directional antennae to reach all the clients in the network.
Fifth, providing directable antennae trained on each of a number of clients may be a waste of resources. For example, if client 112b (FIG. 1C) is running a streaming video application, the improved data communication rate represented by heavy dashed line 116c would be desirable. On the other hand, if client 112b is casually accessing Internet web pages or sending e-mail, the higher data communication rate facilitated by the directable antenna would be unnecessary and could be viewed as a waste of hardware resources and processing overhead.
It would therefore be desirable to provide a system and method that would enhance communication between an access points and its clients in a wireless network. In particular, it would be desirable to improve the data rates available to a plurality of clients without having to include multiple-radio transceivers in the access point. Furthermore, it would be desirable to achieve higher data rates without having to waste bandwidth as a result of resending access point beacons or network messages, across a plurality of antennae that is each coupled to a different transceiver.